According to a conventional occupant weight detecting device, the occupant weight may be detected in error due to the secular deterioration inherent to a load sensor. In order to solve the aforementioned problem, a weight detecting device for a vehicle is disclosed in a Japanese Patent Laid-Open publication No. 2001-21411. The disclosed device is provided with a load sensor equipped to a seat body and a judging means for judging whether or not there is an occupant/object on the seat body. A value detected by the load sensor during no occupant/object on the seat body is set to be an initial load value under an initial condition of the seat body. The disclosed device is further provided with a calculating means for calculating an actual weight by subtracting the initial load value from the value detected by the load sensor.
As described above, the detected value during no occupant/object on the seat body is set to be a drift amount under the initial condition of the seat body so that the value detected by the load sensor is corrected based upon the drift amount. In this case, the condition of the seat body, i.e. whether the occupant/object is on the seat body is judged based upon the fluctuation of the load value detected by the sensor or a vehicle door locked condition.
However, if an object is left on the seat body when the occupant is getting out of the vehicle, the judging means judges that the for an initial load is applied for the seat body even if there is the object on the seat body. Therefore, the correcting process is performed based upon the detected value including the load of the object. Further, when the occupant is taking on the vehicle without the object, the load value is detected in error by the load of the object. That is, the disclosed weight detecting device may be easily affected by external factors such as the object on the seat body. Accordingly, the drift amount under the initial condition of the seat body due to the secular deterioration may not be accurately offset.
The present invention therefore seeks to provide an occupant weight detecting device capable of improving accuracy for offsetting a detected value by a sensor under an initial condition of a seat body.